And during its peak intensifying period Tuesday evening, the storm was much faster, at 20 millibars over just nine hours.
Among the many sights that caught weather watchers’ eyes was a pronounced tail at the apex of band of thunderstorms near the low pressure system’s core. The comma-like squalls converged to a point, resembling the tip of a scorpion’s tail. At the same time, Doppler radar measured winds above the ground pushing 120 mph.
It was a sting jet, a narrow but extremely intense burst of jet stream energy.
The sting jet forms in rapidly deepening low pressure systems, when a band of precipitation wraps back along a cold conveyor belt in a region of exceptional wind energy aloft. Dry air intruding at lower altitudes can undercut this shot of heavy precipitation. It eats away at falling precipitation, drying out the saturated air and carrying the now-chilled river of winds down to the surface.
The formation of a sting jet starts around two to three miles above the ground. When it occurs, very fast winds from the mid-levels of the atmosphere can descend to ground-level.
Observers could see the evaporation at the tip of this band of storms on radar yesterday, about 50 miles east of Ocracoke on North Carolina’s Outer Banks. Within the vicious thunderstorm line, embedded supercells yielded nearly a half dozen simultaneous tornadic circulations at times. This while destructive gusts to 80 mph and large hail stirred up seas over the open ocean. Supercell thunderstorms over the open ocean are extremely rare.
These severe thunderstorms produced thousands of cloud to ground lightning strikes, some of which shot more than a dozen miles into the clear air swirling into the system. It’s unusual for a nor’easter to produce this much lightning -- a sign of a storm increasing in strength at breakneck pace.
The thunderstorms’ updrafts also helped air rise and exit the storm, aiding in its explosive rate of intensification. Winds likely gusted to near 100 mph at the tip of the sting jet, immediately at the point on satellite where the clouds and dry slot meet.
Despite the immense power of sting jets, their existence was not studied until the late 1980s. In October 1987, what was forecast to be a stiff gale surprised the United Kingdom with a lethal swath of 100-120 mph winds. A gust to 135 mph was clocked in Point du Roc, France.
The 22 deaths that occurred elicited sharp criticism over the poorly predicted event. Keith Browning eventually led a team of meteorologists at the University of Reading that reviewed data and developed the concept of sting jets into the early 2000s.